'Nother Master Cylinder Question

So i have a master cylinder out of a '94-04 V6 Mustang. I tried fitting it yesterday, and the booster is way too big. It doesn't fit between the strut tower and firewall. I thought that was odd because those are still Fox cars pretty much. Question is, can i use my stock Zephyr booster, or will I need to find something else?

I thought i remembered seeing this question answered on here, but I can't find it now.

http://www.svo73mm.cjb.net/ and try http://www.veryuseful.com/mustang/tech/brakes/

Hope they have some answers

Stymees'mont wrote:

http://www.svo73mm.cjb.net/ and try http://www.veryuseful.com/mustang/tech/brakes/

Hope they have some answers

Here is a highlight from the link. I'm going to attempt this this weekend.

This part of the install includes the new power booster, master cylinder, and proportioning valve. First, remove the stock master cylinder and pig tails, followed by the stock booster. Many have foregone installation of the massive Cobra power booster because of tall tails of needing to acquire a big hammer and going postal on the strut tower to gain the required clearance necessary to install the monster booster. Even the instructions supplied with the kit note that "some relieving of the strut tower may be necessary". Well, I did not find such to be the case on this 91 LX coupe but sometime in 1989, the strut tower was redesigned so your results may vary. While it was tight, I never had to swing the hammer. Instead, I was fortunate to receive a tip and such proved to be the trick. The power booster is mounted with four studs that fit in holes in the firewall. After getting all the wires, lines, etc. out of the way, I discovered that the booster almost fit. The problem was that I could not slide the studs in straight, but rather they had to go in on an angle due to the size of the booster. This angle resulted in the top right stud (passenger's right) getting caught up in the hole and not allowing the booster to slide in. The trick is to enlarge this hole with a drill or small die grinder. This allows the stud to have more play. Do not remove anymore then necessary or booster alignment problems may result. I took my time and worked the hole, test fit the booster, etc. until I was able to slide the booster in. The total time of my work here was an hour. In fact, the most difficult part was getting up under the dash to remove and reinstall the retaining nuts.

It refers to a Cobra booster going into a '91 Mustang, but in another spot on the page, the guy recommends getting the biggest booster you can.

ZephyrEFI, do you have the rear disc brakes ?

94-04 mustangs are not fox cars. They are sn95 cars.

Rear disc brakes came with the 8.8 I installed in the fall.

'94-04 is also called "Fox4". There are a lot of things that are the same.

ZephyrEFI wrote:

'94-04 is also called "Fox4". There are a lot of things that are the same.

Yeah, like the entire floorpan.

The '94 and later boosters have a slightly different bolt pattern than the '78-'93 cars, and the studs are a weird metric size that takes a special nut that I had a hard time finding. I did a '94 Cobra booster into a friends' '89 GT convertible, and had to drill the four holes oversize to allow the newer booster to go in. And yes, I also had to hammer the strut tower to get it to go in, but it's in an inconspicuous area that you really have to look for - so I wouldn't rule out a future install because of this.

-Mike S.

Good to hear from someone who's done it!

I'm holding out hope there is an SN95 at the junkyard i can snag the nuts from when i go look for driveshafts.

Fought with this for a while today. no luck getting it in so far.

ZephyrEFI wrote:

Fought with this for a while today. no luck getting it in so far.

You will get it. I have faith in ya. Maybe if you need some help, contact me and I can meet up with ya.

Well, no luck at the junkyard. No SN95 and no driveshafts.

Stymee, that's nice of you. You any good at making brake lines?

hell ya, I made all mine for my car. All I need is a booster and master cyl. and I am all set for brakes.

That would be great! We'll work something out by PM.

I'm hoping to hit Johns this weekend and i'll see if they have anything for me. I'd much rather get the exact nuts than try and find them some other way. I'm also hoping to wrestle that brake pedal bracket out from behind the firewall. I think that's what's preventing that booster from going in. If it's out, it will be easier to modify the holes if needed.